Numerical investigation of demountable CFST K-joints using blind bolts

Abstract

Reusing structural elements is an effective way to prompt sustainable development with reduced energy consumption and gas emission. In current practice, steel members can be easily deconstructed and reused whilst the recycling of structural materials in steel-concrete composite construction has been found challenging. With the increasing material consumption in composite construction due to their well-recognized structural benefits, it is essential to explore the demountability of such structures. Limited previous research indicates that there is a lack of understanding or mature design specification for demountable composite connections. This paper thus presents an innovative design of demountable K-joints with concrete-filled steel tubular (CFST) chords and circular hollow section (CHS) braces connected using blind bolts. A detailed finite element analysis (FEA) modelling was established and validated against reported test data on both bolted and welded CFST connections. The model was then used to evaluate the possible failure modes, full-range load-deformation relationships, stress distributions and material interactions for the innovative connections. Behaviour of the demountable CFST K-joints was compared with that of traditional welded ones. Finally, simplified methods for the strength prediction of demountable CFST K-joints were proposed based on theoretical derivation and parametric analysis on the effects of various factors.